A transceiver is a device that can receive and transmit radio radiation. The transceiver is used within many technical fields, such as in radio communication, radio astronomy, radar and microwave technology. The transceiver often includes one or more integrated circuits (ASIC), either totally or partially.
It is normally required in the construction of a transceiver that the transceiver will fulfil a stipulated certification, which relates, of course, to the field of application for which the transceiver is intended. For example, the specification may place requirements on the noise factor of the transceiver and on the submission of spurious radiation, harmonics, etc. At present, it is often necessary to fulfil the specification in the construction of the transceiver, with a good margin due to such uncertainties and temperature variations, random variations in transceiver manufacture, and possibly erroneous matching between different transceiver stages. However, this often results in higher power consumption and normally lengthens the construction time.
In order to fulfil this specification, it is necessary that the transceiver components, in turn, fulfil certain performance requirements. Because of variations in the transceiver components, a newly manufactured transceiver will not always fulfil its specification. It is therefore desirable to be able to test whether or not the transceiver fulfils its specification. U.S. Pat. No. 5,835,850 teaches a transceiver construction that can be tested so as to ascertain whether or not it functions satisfactorily. The transceiver construction includes means for transmitting a test signal throughout the entire transmitter-receiver chain, and to compare this test signal with a received signal and thereby determine whether or not the construction functions satisfactorily. However, if it is found that the construction is unsatisfactory functionally, there seems to be no possibility of determining which construction component or components malfunctions or malfunction. Neither does it seem possible to adjust or calibrate the construction, either in its entirety or with respect to its components.
A known method with which transceiver components can be calibrated is designated an RF-test. An RF-test involves sending specially selected test signals to a transmitter chain in the receiver, wherewith corresponding response signals are received from the radio frequency stage of the transmitter chain. As a result of this special selection of test signals, the components in the transmitter chain can be examined and calibrated, by comparing the test signals with the response signals. A receiver chain in the transceiver is calibrated in a similar fashion, by injecting particularly selected test signals into the radio frequency stage of the receiver chain, wherewith corresponding response signals are received from the baseband stage of the receiver chain. The special selection of test signals enables the receiver chain components to be examined and calibrated on the basis of comparisons of the test signals with the response signals.
However, RF-testing has several drawbacks. RF-testing is expensive and time consuming, among other things because a large part of the signal processing procedure takes place in the radio frequency range. The accuracy achieved when calibrating with an RF-test is relatively poor, particularly with respect to power levels. Moreover, it is difficult to calibrate radio frequency stages in the transmitter chain and in the receiver chain with RF-testing, due to the influence exerted by the equipment utilised in RF-testing.